A. Javed

Performance Analysis of a Microturbine Centrifugal Compressor From a Manufacturing Perspective

Gasturbine part manufacturers are often not involved in the design process. This means opportunities to optimize the design including manufacturing issues are missed. This paper presents a performance analysis of a microturbine centrifugal compressor from a manufacturer’s perspective. A one-dimensional (1D) performance modeling tool has been devised to predict the design and off-design performance by sequentially calculating the processes in the impeller, vaneless diffuser and scroll. Part drawings have been used to obtain the geometric information. Comprehensive two-zone modeling has been applied along with a set of meanline empirical loss models integrated in the secondary zone to estimate the entropy gain. This novel methodology has allowed the calculation of individual impeller loss mechanisms instead of predicting them as bulk. Computational Fluid Dynamics (CFD) has also been used to quantify the secondary flow properties and improve the 1D model. The results have been validated through a comparison with the microturbine test data. A sensitivity analysis has been performed to investigate the influence of geometric changes upon compressor performance. The study is important to develop design for manufacturing capability and optimize the designs for cost-effective manufacturing.Copyright

Optimization of a Centrifugal Compressor Impeller for Robustness to Manufacturing Uncertainties

Compressor impellers for mass-market turbochargers are die-casted and machined with an aim to achieve high dimensional accuracy and acquire specific performance. However, manufacturing uncertainties result in dimensional deviations causing incompatible operational performance and assembly errors. Process capability limitations of the manufacturer can cause an increase in part rejections, resulting in high production cost. This paper presents a study on a centrifugal impeller with focus on the conceptual design phase to obtain a turbomachine that is robust to manufacturing uncertainties. The impeller has been parameterized and evaluated using a commercial computational fluid dynamics (CFDs) solver. Considering the computational cost of CFD, a surrogate model has been prepared for the impeller by response surface methodology (RSM) using space-filling Latin hypercube designs. A sensitivity analysis has been performed initially to identify the critical geometric parameters which influence the performance mainly. Sensitivity analysis is followed by the uncertainty propagation and quantification using the surrogate model based Monte Carlo simulation. Finally, a robust design optimization has been carried out using a stochastic optimization algorithm leading to a robust impeller design for which the performance is relatively insensitive to variability in geometry without reducing the sources of inherent variation, i.e., the manufacturing noise.

Modification of Standard K-ε Turbulence Model for Analysis and Design Refinement of Fuel Ejector Pump

*† , In this paper flow analysis and design refinement of a fuel ejector pump is done by using Computational Fluid Dynamics technique. The flow inside the ejector pump is modeled as incompressible, steady and turbulent that is governed by the RANS system of equations along with two-equation standard K-e turbulence model for closure. The comparison of computed results with test data indicates that the default values of constants of the K-e turbulence model need adjustment due to complex nature of turbulent flow inside the pump. The values of these constants are then optimized for the unique flow field inside the fuel ejector pump in order to computationally reproduce the test data. Based on these optimized constants, detailed flow field analysis is done that highlight a possible improvement area in pump design. This design refinement is also computationally evaluated and an improvement in pump performance is predicted.

Evaluation of the Influence of Volute Roughness on Turbocharger Compressor Performance From a Manufacturing Perspective

This paper presents a comprehensive surface roughness evaluation of a mass-produced turbocharger centrifugal compressor for automotive application. The aim is to study the impact of surface roughness on compressor performance and manufacturability of the volute. Surface roughness data for different components has been obtained from drawing specifications and sample measurements. Detailed compressor performance evaluation has been made in three parts using CFD. In the first part, the overall compressor performance variation has been simulated from stall to choke over a speed line; initially with all smooth surfaces and later, with rough surfaces. The second part decomposes the performance variation into its sources by simulating each compressor component individually with its specific roughness. Moreover, a performance sensitivity analysis has been conducted to identify the components most responsive to limited surface roughness deviation. In the third part, the volute is subdivided into five sections and a performance sensitivity analysis has been performed by sequentially varying the surface roughness for each section within a particular deviation range. The analysis revealed the sections which essentially require smoothing via sand core coating. Lastly, the roughness specifications have been reviewed especially for the volute, keeping in view the benefits the new specifications may have on overall compressor performance and manufacturing costs.Copyright

Optimization of a Centrifugal Compressor Impeller Design for Robustness to Manufacturing Uncertainties

Compressor impellers for mass-market turbochargers are die-casted and machined with an aim to achieve high dimensional accuracy and acquire specific performance. However, manufacturing uncertainties result in dimensional deviations causing incompatible operational performance and assembly errors. Process capability limitations of the manufacturer can cause an increase in part rejections, resulting in high production cost. This paper presents a study on a centrifugal impeller with focus on the conceptual design phase to obtain a turbomachine that is robust to manufacturing uncertainties. The impeller has been parameterized and evaluated using a commercial computational fluid dynamics (CFD) solver. Considering the computational cost of CFD, a surrogate model has been prepared for the impeller by response surface methodology (RSM) using space-filling Latin hypercube designs. A sensitivity analysis has been performed initially to identify the critical geometric parameters which influence the performance mainly. Sensitivity analysis is followed by the uncertainty propagation and quantification using the surrogate model based Monte Carlo simulation. Finally a robust design optimization has been carried out using a stochastic optimization algorithm leading to a robust impeller design for which the performance is relatively insensitive to variability in geometry without reducing the sources of inherent variation i.e. the manufacturing noise.Copyright